Ec primer coating for paper and paperboard

ABSTRACT

Disclosed are energy curable primer compositions for use on uneven substrates such as paper or board to help create a non-porous, smooth, print-receptive surface for subsequent in-line or off-line application of metallic or special effect inks for generating a superior appearance such as a mirror-like metallic or other special effect for promotional or high-value packaging applications. Compositions suitable for low odor and low migration indirect contact food, tobacco, or pharmaceutical product packaging are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 14/760,380 filed Jul. 10, 2015, which is a § 371 National Stageapplication of PCT/US2014/011601 filed Jan. 15, 2014, which claims thebenefit of U.S. Provisional Application No. 61/753,576 filed Jan. 17,2013, all of which applications are incorporated herein by reference inthe entirety.

FIELD OF THE INVENTION

The present invention relates to energy curable primer compositions thatshow over-printability and interlayer adhesion with inks or overprintlacquers as well as flexibility for use in packaging.

BACKGROUND OF THE INVENTION

Special effects such as highly reflective metallic-effect packaging isoften used in retail and promotional packaging designs to promote,attract and draw increased customer attention and thereby increase salesand services of packaged products. Toward this end, traditional printingmethods may utilize a pre-processed metallic foil or metalized filmlaminated to paper or paperboard substrate such as used to producefolding carton boxes for goods. In this method, the metallic substrateis relatively expensive compared to standard quality white paper orpaperboard used for printing standard quality graphic designs forfolding carton packaging. In addition, metallic foil or metalized filmlaminated paper or paperboard is typically overprinted over asignificant surface area with opaque white ink covering the metalliceffect, to provide sufficient area of a neutral white base-coat forcolored graphics to be printed, while leaving less than 100% of themetallic surface uncovered to create the intended visible metalliceffect.

In a more efficient approach, packaging requiring a metallic effect canbe printed only in the required regions on standard quality white coatedpaper or paperboard using a metallic effect printing ink. Low viscosityliquid printing inks applied onto porous and non-smooth substratespenetrate and soak into the porous substrate, and/or dry in a non-smoothlayer following the non-smooth surface contours of the substrate,resulting in a visible and measurably low-reflectivity,non-aesthetically pleasing metallic appearance compared to the highreflective qualities of metallic foil or metalized film. The use ofprimers is typically recommended in order to help improve the metallicappearance.

Although the concept of using a primer to improve the surface of asubstrate before applying an ink is not new, there is very limited priorart related to energy curable primers that are effective at improvingmetallic appearance. A recent patent application from ShorewoodPackaging/International Paper (WO2012099698) discloses a method toproduce a package with a metallic appearance including applying anenergy curable primer and a metallic ink. However, there is noinformation provided regarding the composition of suitable primers thatwill enable the creation of packages having the desired metallicappearance to replace foil stamping or use of fully metalized board suchas board laminated with a metalized film (“Met-Pol” board) or boardlaminated with a thin aluminum foil (“Transmet” board).

Achieving superior reflectivity and brilliance index requires specialprimer characteristics which are not disclosed by Shorewood. Inaddition, metallization primers disclosed in the prior art, such as theclear undercoat primer from Jetrion disclosed in US2007/076069 and U.S.Pat. No. 7,891,799, do not provide the same level of temperaturedependency of the viscosity exhibited by the primers of the presentinvention. This particular rheological behavior in the primers of thepresent invention brings superior leveling capability at applicationtemperature with reduced board penetration. As a result, the primer hassuperior gloss retention over a large range of anilox volume (whichrelates to applied coating weight) going from 15 bcm (billion cubicmicrons/in²) to 10 bcm and 5 bcm. The primers of the present inventionpreferably have a viscosity reduction % of over 55% between 25° C. and45° C. whereas the prior art primer typically shows about 27%.

In addition, primers from the prior art are very sensitive to thesurface they are printed onto as illustrated in the gloss differences onBYK Penopac charts between the primer on the white coated part of thechart compared with the white uncoated part of the chart. Thatsensitivity is further increased with lower anilox volumes as seenillustrated in Example 2 below.

Accordingly, the prior art also fails to disclose primer formulationswhich would be suitable for use in packaging where organolepticcharacteristics such as odor and migration are important (e.g. food,tobacco, and pharmaceutical packaging). By selecting acrylate monomersand oligomers having certain properties and/or with a MW of preferablyat least 300 g/mol in combination with appropriate additives and, ifapplicable, photoinitiator package, one can produce an effectivemetallization primer with low odor and low set-off migrationcharacteristics (per testing from EU directive No. 10/2011).

SUMMARY OF THE INVENTION

The present invention provides a primer composition comprising:

(a) an acrylic monomer comprising C—O—C and C═C functional groups; and

(b) an acrylic oligomer comprising C—O—C and C═C functional groups,wherein said primer composition is energy curable and the calculatedratio of C—O—C to C═C functionality in the sum of the acrylic monomerand acrylic oligomer is greater than 1.6.

The present invention also provides a printed article comprising theprimer composition of the present invention.

The present invention further provides a method of printing an energycurable primer composition comprising applying to a substrate the primercomposition of the present invention.

The present invention also provides a method for forming a brilliantmetallic coated paper material comprising:

(a) applying a layer of the primer composition of the present inventionto a paper surface of the paper material;

(b) curing the layer of the primer to create an ink receptive interfacelayer;

(c) applying a reflective metallic ink including a plurality ofreflective particles to at least a portion of the cured primer layer;and

(d) drying the metallic ink to form a reflective metallic ink layer onthe cured primer.

These and other objects, advantages, and features of the invention willbecome apparent to those persons skilled in the art upon reading thedetails of the methods and formulations as more fully described below.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a SEM cross-section of a Leneta chart coated with the curedExample 1 primer using a 15 bcm anilox and overprinted with metallic VMPink SC17604. The image shows the smooth and uniform layer created by theprimer with a thickness of about 4.5 microns on top of the board and howthe surface is improved compared with the board surface itself.

DETAILED DESCRIPTION OF THE INVENTION

The present invention describes energy curable primer compositions foruse on uneven substrates such as paper or board to help create anon-porous, smooth, print-receptive surface for subsequent in-line oroff-line application of metallic or special effect inks for generating asuperior appearance such as a mirror-like metallic or other specialeffect for promotional or high-value packaging applications.Compositions suitable for low odor and low migration indirect contactfood, tobacco, or pharmaceutical product packaging are also disclosed.

The liquid primer compositions of the present invention are energycurable (UV or E-Beam), can be applied substantially solvent-free (<500ppm), or with evaporative drying/UV or E-Beam curing if diluted usingsolvent or water, and are preferably formulated at gravure or flexoprinting application viscosity for curing by free radical polymerizationinitiated by an electron beam or suitable actinic radiation with orwithout the use of nitrogen-inerted atmosphere conditions. While thecompositions are preferably applied by flexo or gravure processes, it isunderstood that the compositions could also be modified to make themsuitable for use in other deposition methods (e.g. spray coating, inkjet, lithographic, roll coating, curtain coating, etc.). With apreferred low surface tension, the liquid primers exhibit good wettingcharacteristics over paper or board substrates. The cured primer-coatedsubstrate may be further processed in-line on subsequent printingstations, or stored, or processed downstream or off-line, depending onapplication and operational needs of the printer-converter. The primerspreferably show excellent over-printability and interlayer adhesion withinks or overprint lacquers as well as flexibility for use in packaging.

Compared to prior art, in certain types of primers requiring a lowerviscosity formulation, for example flexo- and gravure-applied primersformulations, the compositions of the present invention preferablyexhibit a much larger viscosity reduction as temperature increases(typically greater than 50% drop in viscosity between 25° C. and 45° C.compared to less than 30% for the prior art). Such rheological behaviorallows for primers to optionally be applied at an elevated temperature,provide excellent printing and leveling while at elevated temperaturewhile having limited penetration into the board. Such behavior is alsoillustrated by the more robust gloss retention performance of theprimers at different coating film weights compared to the prior artformulations. In one embodiment, the compositions have also shownlimited gloss differences when printed over a coated portion of a BYKPenopac chart or an uncoated BYK Penopac chart. Such characteristics mayresult in improved primer transfer efficiency during printing.

Effective primer compositions compatible with use in packagingapplications where organoleptic aspects such as odor and taste areimportant (e.g., food or tobacco packaging) are also presented. Whencured in a commercially printed packaging structure (e.g. thosecomprising paper or paperboard substrate+primer+suitable metallic orcolored inks+suitable overprint varnish or lacquer), the set-offmigration measured is preferably less than their specific migrationlimit (SML) or less than 10 ppb for residual components without SML,thus ensuring compliance with European Food Safety regulations per EUdirective No. 10/2011.

The ability to spot-apply a UV or EB curable primer coating onto astandard quality paper or paperboard, followed by a highly reflectivemetallic ink, only where it is required by the graphic design, allowsfor more efficient packaging designs and improved yield and processefficiencies to printer-converters over comparable packaging producedusing traditional metalized laminated paper or paperboard substrateshaving 100% coverage of a metallic foil or a metalized film layer, whichare typically partially overprinted with white ink and colored inks inorder to create the full range of required commercial graphics. It alsoallows similar advantages over other comparable metallic graphic effectsproduced by metallic hot or cold foil stamping onto printed materials.

The primers of the present invention provide higher gloss at lower filmweight and are more robust to differences in substrate porosity. Thisallows converters to make a more efficient use of the primer (bettermileage without significant loss in gloss) and adapt more easily tochanges in board porosity or surface energy. Also, the preferred highdispersive surface energy of the cured primer makes it an excellentsurface for overprinting with solvent based inks (such as colored orspecial effect inks) to create more appealing graphics and thereforehelp converters/brand owners create packages or labels with more shelfappeal.

UV or EB curable coatings with viscosity low enough to be suitable forflexo or gravure applied coating typically contain low molecular weight,low viscosity, mono-, di or tri-acrylate monomers such as 1,6-Hexanedioldiacrylate, Dipropyleneglycol diacrylate, Tripropyleneglycol diacrylate,Trimethylolpropane triacrylate, or similar type, leading to a highresidual cured odor and significant residual migratable components fromcured films, making them unsuitable for food or tobacco packagingapplications. Alternative, more acceptable acrylate monomers andoligomers are frequently too viscous to formulate into gravure appliedcoatings. Dilution of acrylate functionality with water, solvent, orplasticizer to achieve an acceptable viscosity can lead to a reductionin efficiency or speed of curing, loss of cured film toughness ordurability, surface defects such as pinholes or craters, or retention ofundesirable solvent in the cured film. The use of surface tensionlowering surface active agents such as polydimethylsiloxanes, siliconeoils, or other surfactants to eliminate surface defects in primercoatings also reduces the surface energy of the cured primer film belowthat of other inks intended to print on top of the primer, producingpoor ink transfer and poor interfilm adhesion between inks and primer.To achieve efficient ink transfer from the printing medium, whether itis an engraved cylinder or a processed plate, to the substrate, thesurface energy of the solid substrate is preferably higher than thesurface tension of the liquid ink being transferred onto it in order forthe ink to wet and spread onto the surface. In the case of primer-coatedpaper or paperboard, the cured primer film is the substrate for the nextapplied ink to wet and transfer onto.

The present invention discloses that certain parameters are preferred inthe selection of the best energy curable primers for porous unevensubstrates such as paper and board. These parameters are even morepreferred in the case of gravure printable primers, where viscosity istypically lower than with flexo primers, which increases the potentialrisks of the primer penetrating into the board and therefore producing aless attractive finish.

In one embodiment, the current invention also introduces gravureprintable primers with a viscosity at 45° C. between 17 and 25 cPsmeasured at 10 reciprocal seconds (sec⁻¹) with a coaxial cylinder(Couette) geometry on a TA Instruments AR-1500 rheometer using innercylinder diameter 28 millimeters and outer cylinder diameter 30millimeters and 1 millimeter gap. The viscosity reduction between 25° C.and 45° C. of these formulations preferably exceeds 55%.

In another embodiment, the ratio of C—O—C to C═C functionality in themonomer and oligomer fraction of the primer formulation is >1.6 meq/gand preferably >1.8 compared to 1.5 for the prior art formula. Thisratio relates to a higher degree of alkoxy functionalities in thecoating which is associated with a lower static surface tension for thecoating 33 mN/m) which further helps wetting onto the substrate.

In a preferred embodiment, the liquid static surface tension of the UVor EB primer is 33 mN/m at 20° C., measured using a Cahn DCA-312tensiometer; Wilhelmy plate technique using glass plate 25×25 mm, ˜0.1mm thick, temperature 20° C.; and the cured primer film has a dispersivesurface energy >34 mN/m and preferably ≥37 mN/m.

In yet another embodiment, the current invention disclosure alsointroduces gravure printable primers with a viscosity at applicationtemperature ranging between 15 and 65 cPs and preferably between 17 and25 cPs measured at 45° C., and a viscosity reduction factor between 25°C. and 45° C. greater than or equal to 50%. In a preferred embodiment,the primer will have a viscosity at 45° C. between 17 and 25 cPsmeasured at 10 reciprocal seconds (sec⁻¹) with a coaxial cylinder(Couette) geometry on a TA Instruments AR-1500 rheometer using innercylinder diameter 28 millimeters and outer cylinder diameter 30millimeters and 1 millimeter gap.

In applications where organoleptic characteristics such as odor andsmell are important like food or tobacco packaging, the monomers arepreferably selected with a MW of preferably at least 300 g/mol incombination with approved additives and, if applicable, photoinitiatorpackages, in order to produce an effective metallization primer with lowodor and low set-off migration characteristics (per testing according toEU directive No. 10/2011).

The liquid primers of the present invention are preferably formulatedsuch that they may be cured using actinic radiation e.g. UV in air orwhen inerted with nitrogen or other gas to displace and reduceatmospheric oxygen concentration, or EB preferably in conditions whereoxygen concentration does not exceed 200 ppm, to yield a cured dry,over-printable film preferably having the following characteristics onLeneta N2A-3 charts when printed using a TMI Flexiproofer with a 15 bcmanilox.

Total surface energy after curing is preferably ≥37 mN/m as measuredusing contact angle measurements of probe liquids (water anddi-iodomethane) using a Fribro 1100 DAT instrument. Dispersive and Polarcomponents were calculated by splitting the total surface energy usingFowkes' theory geometric mean approach.

Also preferably, gloss after cure at 20° angle is >55 and Gloss at 60°angle is >83 as measured using a BYK-Gardner micro-TRI-gloss meter.

Once overprinted with a suitable silver metallic ink (e.g. Sun ChemicalSC17604 MIRRORTECH® S) and applied with a #3 Meyer wire-wound coatingbar, primed metalized surfaces will preferably exhibit a total visiblelight reflectance greater than or equal to 64 with a brilliance indexequal to or greater than 86%.

The primer compositions of the present invention are preferably designedfor performance in gravure or flexo application without the need foraddition or dilution with other materials or solvents.

The primer formulations are preferably essentially solvent-free (<500ppm), include energy curable monomers and/or oligomers, optionally aphotoinitiator package (which may include an amine synergist),optionally low levels of additives such as surfactants; flow/levelingagent and/or defoamer (preferably non-silicone). Optionally primerformulations may also include colorants, tinting packages, or visualeffect pigments, to improve graphic reproduction or enhance visualimpact of the graphic design.

The formulation components are selected such that: (a) the reduction inprimer coating viscosity measured at 10sec⁻¹ between 25° C. and 45° C.is equal to or greater than 50%; (b) the cured primer applied using aFlexiproofer with a 15 bcm anilox on Leneta N2A-3 chart has a totalsurface energy greater than or equal to 37 mN/m; and/or the gloss of theprinted primer after cure at 20° angle is >55; and gloss at 60° angle is>83.

Selection of low viscosity monomer or oligomers with a higher molecularweight, low viscosity, and high surface tension are preferred for thecorrect gravure application viscosity, fast curing, optimum cured filmsurface energy, and low post-cure migration potential of residualcomponents.

Selection of optimum surface active agents for control ofprimer-substrate wetting, flow and leveling, as well as antifoaming anddefoaming capability, are preferred for a smooth and defect-free surfaceof the liquid primer as it is applied onto the paper or paperboardsubstrate, resulting in a preferred dispersive surface energy whencured >37 mN/m.

In another embodiment, the coating formulation and in particular theadditive package is selected such that the cured coating exhibitssuperior gloss retention over a range of anilox volumes from 15 to 5 bcmwhen printed onto BYK Penopac 2817 charts. Superior gloss retention isdefined as a gloss reduction of less than 10 points at a 60° angle and agloss reduction of less than 20 points at a 20° angle when changing from15 bcm to 5 bcm anilox. Examples of suitable additive package includepolyacrylate flow and leveling promoters such as Tego Flow 425, TegoFlow 300, Tego Flow 370, Tego Wet 270, BYK 361 and BYK 3455.

In a further embodiment, the additive package is preferably selected toprovide robust gloss performance over coated and uncoated board asillustrated by gloss differences between the cured coating over whitecoated area of the BYK Penopac 2817 chart compared with cured coatingover the white uncoated area of the chart. Preferred compositions showat a 60° angle a gloss difference of less than 2 at 15 bcm and less than4 at 10 bcm.

The effectiveness of the primer of the present invention was alsodemonstrated on thin coated paper (less than 70 gsm total) such as thatused for beer labels. The primed papers were metalized with SC17604 andexhibited similar brilliance and metallic appearance comparable to beerlabels prepared using vacuum metallization. Vacuum metallization is atechnology which requires the label to be first primed before vacuummetallization then overprinted with a lacquer that provides a suitableprint surface for printing inks which will ultimately be covered by alacquer. With the primer of the present invention, the metallizationprimer is followed by the silver inks and directly printable withgraphics and overprint varnish thus eliminating at least one layer ofvarnish and the associated waste of vacuum metallization.

The primers of the present invention can also be used to improve thesurface characteristics of thermoplastic films or board with acoextruded plastic layer (such as PE) and therefore the appearance ofgraphics printed on top of the primer. Examples of such substratesinclude for example milk cartons which are traditionally difficultsubstrates to print with high quality. The primers of the presentinvention can also be used on other substrates such as polymeric types,cellulosic, wood, metal, etc.

The primers of the present invention may also include colorants.Suitable colorants include, but are not limited to organic or inorganicpigments and dyes. The dyes include but are not limited to azo dyes,anthraquinone dyes, xanthene dyes, azine dyes, combinations thereof andthe like. The pigments include but are not limited to coated or uncoatedmica or other inorganic metal oxides, pearlescent, opalescent,angle-dependent and other photonic pigments, carbon black, metal ormetallic alloys such as aluminum or bronze, and organic pigments.

As with most coating compositions, additives may be incorporated toenhance various properties. A partial list of such additives includesbut is not limited to adhesion promoters and cross-linkers such as amineor amino-functional compounds, organo-metallic compounds such astitanate, zirconate, phosphate, or other inorganic, or organicacid-functional compounds, light stabilizers, de-gassing additives, flowpromoters, defoamers, antioxidants, UV stabilizers, surfactants,dispersants, plasticizers, rheological additives, waxes, silicones,other surface or interfacial modifiers, etc.

Although a solvent gravure-applied silver effect ink is used to generatemetallic effects with the primer examples given, effective results canalso be achieved using other printing application processes for theeffect ink over the primer, including but not limited to waterbased,energy curable, flexo, gravure, inkjet, offset, and other commonlyapplied printing or coating methods.

The primer compositions of the present invention have demonstrated asshown below the ability to provide more brilliant metallic appearancecompared to compositions known in the prior art. These rapid curingprimer coatings on non-smooth and porous substrates allow a substratesurface to be modified, becoming a non-porous, level and glassy-smooth,print-receptive surface for application of a low viscosity liquidmetallic effect ink that leads to ink drying with a near mirror-likesurface appearance closely resembling the visual reflective effect ofmetal foil or metalized film. Substrates primed with these compositionsmay also be used for other applications where the primer can beoverprinted with inks or other colored or special effect inks to providea more vibrant visual effect or an overall improvement in gloss orgraphics appearance.

The following examples illustrate specific aspects of the presentinvention and are not intended to limit the scope thereof in any respectand should not be so construed.

EXAMPLES 1-9

A series of EB and UV primer formulations were compared for gloss at 20°and 60° , and for Brilliance Index. Prints were made by first printingeach of the primers using a TMI Flexiproofer with a 15 bcm anilox onto aLeneta N2A-3 chart, curing the primer, and then overprinting withSC17604 acetate solvent-based vacuum metalized pigment silver ink fromSun Chemical applied with a Meyer #3 bar on Leneta Form N2A-3 (overwhite board). Brilliance Index of Transmet and Metpol board referencestandards was also measured.

TABLE 1* Finished ink formulations. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6Ex. 7 Ex. 8 Ex. 9 (Inven- (Inven- (Inven- (Inven- (Inven- (Compar-(Compar- (Compar- (Inven- tive) tive) tive) tive) tive) ative) ative)ative) tive) 5EO-PETTA 50.00% 3EO-TMPTA 74.30% 74.30% 74.30% 54.10%54.10% 50.00% 45.80% 45.10% GPTA 20.70% 2PO-NPGDA 25.00% 25.00% PEG200DA25.00% 25.00% HDDA 38.00% 34.00% 34.00% TPGDA 25.00% DPGDA 2EO-BPADA10.00% PHOTOMER 5006 12.00% 12.00% 12.00% 12.00% 10.00% MDEA 4.00%OMNIPOL BP 8.00% EBECRYL P-39 4.00% 4.00% 4.00% 4.00% IRGACURE 29594.00% 4.00% ESACURE ONE 1.00% IRGACURE 184 4.00% 4.00% 4.00% TPO 4.00%GENORAD 16 0.20% 0.20% 0.20% 0.20% 0.20% TEGOFLOW 370 0.50% 0.50% 0.50%0.50% 0.50% 0.50% BYK A-535 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% UVViolet Toner 0.10% Total 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%100.00% 100.00% 100.00% *Ex. 1 - EB Gravure Ink; Ex. 2 -EB Gravure Ink;Ex. 3 - EB Gravure Ink; Ex. 4 - UV Gravure Ink; Ex. 5 - UV Gravure Ink;Ex. 6 - UV Clear Undercoat from US2007/076069; Ex. 7 - UV ClearUndercoat from US2007/076069 + photoinitiators; Ex. 8 - UV ClearUndercoat from US2007/076069 + photoinitiators and flow additives; Ex.9 - UV Flexo Ink.

TABLE 2 Ink & cured ink film properties{circumflex over ( )}. Ex. 1 Ex.2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 (Inven- (Inven- (Inven-(Inven- (Inven- (Compar- (Compar- (Compar- (Inven- tive) tive) tive)tive) tive) ative) ative) ative) tive) C—O—C meq/g 16.2 13.5 14.3 14.511.7 10.4 12.8 C═C meq/g 6.9 6.7 7.1 5.6 5.5 6.9 5.6 C═O meq/g 6.9 7.57.1 6.0 6.6 6.9 5.9 C—O—C/C═C ratio 2.4 2.0 2.0 2.6 2.1 1.5 2.3 Low OdorFormulation Yes Yes No Yes Yes No No No Yes TA Couette 25° C., cPs 48.647.6 42.8 63.7 30.1 23.5 303 TA Couette 45° C., cPs 19.1 18.9 17.7 24.212.9 17.2 82.6 Viscosity % drop 25-45° C. 60.7% 60.3% 58.6% 62.0% 57.1%26.8% 72.7% Liquid SST 20° C., mN/m 29.5 32.3 28 30.2 30.8 34.9 37.1Liquid DST 23° C., mN/m 37.5 35.6 35.5 38.1 39.3 36.9 58.1 CuredDispersive, m/N/m 37 38 38 42 42 42 43 Cured Polar, mN/m 7 7 9 3 4 4 7Cured Total, mN/m 44 45 47 45 46 46 50 Y-SCI 69.37 69.02 69.03 64.5958.86 62.82 65.35 Brilliance Index 88.7% 88.65% 88.75% 86.15% 80.3%83.35% 86.8% w/SC17604 Silver Gloss 20° 15 BCM Anilox 63.4 59.2 61.762.2 56.3 53.8 57.7 Gloss 60° 15 BCM Anilox 86.2 83.7 85.1 87.8 86 83.987.5 COF Static 0.459 0.446 0.561 0.354 0.312 0.398 0.473 COF Kinetic0.365 0.366 0.466 0.312 0.265 0.316 0.38 {circumflex over ( )}Note:adhesion and flexibility of all printed samples was found to beacceptable

TABLE 3 Chemical names and description of ingredients in Table 1.Material Chemical Name/Description 5EO-PETTA Ethoxylated pentaerythritoltetra-acrylate 3EO-TMPTA Ethoxylated trimethylolpropane tri-acrylateGPTA Glycerol propoxy tri-acrylate 2PO-NPGDA Propoxylatedneopentylglycol di-acrylate PEG200DA Polyethylenglycol (200) di-acrylateHDDA Hexanediol di-acrylate TPGDA Tripropyleneglycol di-acrylate DPGDADipropyleneglycol di-acrylate 2EO-BPADA Ethoxylated bisphenol-Adi-acrylate PHOTOMER 5006 Amine mono-acrylate MDEA Methyldiethanolaminephotosynergist OMNIPOL BP Oligomeric Benzophenone-PI EBECRYL P-39Benzophenone derivative-PI IRGACURE 2959**PI-4-(2-hydroxyethoxy)phenyl-(2- hydroxy-2-propyl)ketone ESACURE ONEPI-Oligo[2-hydroxy-2-methyl-1- [4-(1-methylvinyl)phenyl]propanone]IRGACURE 184 PI-1-Hydroxy-cyclohexyl-phenyl-ketone TPOPI-2,4,6-trimethylbenzoyldiphenylphosphine oxide GENORAD 16 Proprietaryinhibitor TEGOFLOW 370 Polyacrylate additive/flow promoter BYK A-535Proprietary defoamer (acrylic polymer) UV VIOLET TONER 0.1% PigmentViolet 23 dispersion in 5EOPTTA **PI = Photoinitiator

Examples of 3-Ethoxy-trimethylolpropane triacylate include: TMPEOTA,Cytec Surface Specialties; Photomer 4149, IGM Resins; EM2380, EternalChemical Co.; Miramer 3130, Miwon Specialty Chemical Co.; and SR454,Sartomer Company. Examples of Polyethyleneglycol (200) diacrylateinclude: Photomer 4050, IGM Resins; EM224 Eternal Chemical Co.; Miramer282, Miwon Specialty Chemical Co.; and SR259, Sartomer Company. Examplesof 2-Propoxyneopentylglycol diacrylate include: Photomer 4127, IGMResins; EM2251 Eternal Chemical Co.; Miramer M216, Miwon SpecialtyChemical Co.; and SR9003, Sartomer Company. Examples of Polyacrylateflow and leveling additive include: Tego Flow 425, Tego Flow 300, TegoFlow 370, and Tego Wet 270, Evonik Industries; and BYK 361-N, and BYK3455; BYK USA Inc. Examples of Polymeric defoamer/deaerator additiveinclude: BYK-A 535, BYK USA Inc.; and Tego Airex 920, Evonik Industries.

Addition of appropriate low odor, low migration, and commerciallyavailable free-radical photoinitiators and photosynergists can convertthese examples to equally effective UV curable primer coatings. Examplesof such free-radical photoinitiators and photosynergists include:Irgacure 127, BASF Corp.; Omnipol Series, IGM Resins; Speedcure 7000Series, Lambson Ltd.; Genopol Series, Rahn USA Corp.; and CN3715LM,Sartomer Company.

The following Table 4 illustrates physical properties of a partial listof preferred monomers and oligomers for use in the primers of thepresent invention. Table 4 discloses only a partial list, and any othermaterial exhibiting the expressed favorable characteristics of surfaceenergy, gloss retention, and viscosity decrease during heating wouldalso be preferred. Functionality density has been calculated based onthe theoretical structure of the monomer/oligomer material assuming 100%purity.

TABLE 4 Physical properties of a partial list of preferred monomers andoligomers for use in the primers of the present invention C—O—C²/ C—O—CC═C/ C═C C═O/ C═O Viscosity¹ Material M.W.¹ mole meq/g mole meq/g molemeq/g R.I.¹ cPs, 25° C. 5EO-PETTA 528 9 17.05 4 7.58 4 7.58 1.4711 1503EO-TMPTA 428 6 14.02 3 7.01 3 7.01 1.4689 60 GPTA 480 6 12.50 3 6.25 36.25 1.4605 95 2PO-NPGDA 328 4 12.20 2 6.10 3 9.15 1.4464 15 PEG200DA302 7 23.18 2 6.62 2 6.62 1.4639 25 HDDA 226 2 8.85 2 8.85 2 8.85 1.45610 TPGDA 258 4 15.50 2 7.75 2 7.75 1.4606 15 DPGDA 242 3 12.40 2 8.26 28.26 1.4502 10 2EO-BPADA 512 4 7.81 2 3.91 2 3.91 1.534 1400 PHOTOMER5006 650 6 9.231 1 1.54 3 9.55 70 ¹Molecular weight, refractive index(R.I.) and Viscosity are from supplier data. ²Calculated molarcomposition and milliequivalent/gram (meq/g).

For reference, representative samples of unprinted Met-Pol and Transmetboard were obtained as illustrated in Table 5.

TABLE 5 Parameter Met-Pol board Transmet board Y_(SCI) ~83 ~83Brilliance Index ~90% ~96%

Brilliance Index Test Method

Total visible light reflectance (Y) and Brilliance Index were measuredusing an X-Rite XP-64 sphere spectrophotometer using a 4mm aperturesetting. Measurements were taken according to ASTM E313-98 in bothspecular component included (SCI) and specular component excluded (SCE)modes. The brilliance index which indicates how metallic the sampleappears based on the degree of specular light reflection was calculatedfrom the following equation:

Brilliance Index (%)=[Y _(SCI) −Y _(SCE) ]/Y _(SCI)*100

UV and EB primers of this invention preferably have a characteristictemperature viscosity dependency showing much larger reduction inviscosity between 25° C. (ambient room temperature) and 45° C. (typicalmaximum application temperature). These formulations provide highergloss, total visible light reflectance, and brilliance index comparedwith prior art metallization undercoat/primer in US2007/076069 (Examples6-8). Examples 1 and 2 illustrate gravure printable EB formulations ofthe present invention with monomers and oligomers having individualmolecular weight >300 grams per mole for odor and taste sensitivepackaging applications. Example 3 illustrates a gravure printable EBformula which is not preferred for odor and taste sensitive packaging.Examples 4 and 5 illustrate gravure printable UV formulations of thepresent invention with monomers and oligomers having individualmolecular weight >300 grams per mole for odor and taste sensitivepackaging applications. Example 9 is an example of flexographicprintable formulation of the present invention with low odorcharacteristics. In practical applications of low odor formulations, theprimer would be overcoated with inks and overprint varnish or lacquer,and be expected to demonstrate <10 ppb offset migration based on testingprotocols using Tenax food stimulant following European Commissionregulation EU 10-2011.

Gloss Results

Several UV primer formulations were applied using a TMI UV Flexiproofer100 onto BYK Penopac charts 2817. The charts had white coated anduncoated regions. Gloss 60° was measured using a BYK-Gardnermicro-TRI-gloss meter over both areas. The samples were cured with a UVlamp intensity at 100 W/in at a speed of 200 fpm.

TABLE 6 Gloss results of primer formulations Ex. 4 Ex. 6 Ex. 7 Ex. 8 BYKPenopac White Coated Area Gloss 60° results 15 BCM 91.9 92.9 91.3 90.610 BCM 91.7 90.2 88.9 90.0  5 BCM 85.02 56.70 56.95 84.40 Gloss 20°results 15 BCM 62.1 70.0 70.0 68.9 10 BCM 66.0 64.0 61.2 64.6  5 BCM49.4 21.4 23.6 48.2 BYK Penopac White Uncoated Area Gloss 60° results 15BCM 91.2 54.7 63.0 89.6 10 BCM 88.9 32.5 39.3 87.2  5 BCM 73.5 25.6 25.163.5 Gloss 20° results 15 BCM 62.7 25.2 34.4 59.9 10 BCM 52.7 11.2 13.852.7  5 BCM 30.6 4.5 4.2 22.3

The results show the superior gloss retention of an example of primerfrom of the present invention (Example 4) compared with the primer fromthe prior art (Example 6) and variants of the Example 6 formulation(Examples 7 and 8) using the same photoinitiator and photoinitiatorlevel as Example 4 and also a flow additive. The additional results showthat by substituting the photoinitiator and introducing a flow additiveto match the additive package from Example 4, the 60° gloss retention onPenopac chart 2817 is greatly improved looking at both the retention onthe white coated area as well as the difference in gloss between thecoated and uncoated area.

These examples shows that the coating formulation and in particular theadditive package can be selected such that the cured coating exhibitssuperior gloss retention over a range of anilox volumes from 15 to 5 bcmwhen printed onto BYK Penopac 2817 charts. Superior gloss retention isdefined as a gloss 60° reduction of less than 10 points and a gloss 20°reduction of less than 20 points when changing from 15 bcm to 5 bcmanilox. One example of a suitable additive package includes polyacrylateflow promoters such as Tego 370, but other suitable flow additives couldbe used. Furthermore, the additive package can also help provide morerobust gloss performance over coated and uncoated board as illustratedby gloss differences between the cured coating over white coated area ofthe BYK Penopac 2817 chart compared with cured coating over the whiteuncoated area of the chart. Preferred compositions show a gloss 60difference of less than 2 at 15 bcm and less than 4 at 10 bcm.

Typically the UV or EB primer is applied as the first layer on thesubstrate, followed by metallic silver and other inks. In some practicalapplications, there may be a need for UV or EB primers to be appliedover dried inks without re-wetting or dissolving the inks disrupting theimage quality of printed graphics. Example 2 is an example of a primercomprising a monomer and oligomer composition having low solvency fornitrocellulose based gravure inks. A practical test for primer-inkcompatibility involves applying a droplet of primer onto the surface ofdry ink, wiping the excess fluid after several minutes, and assessingthe degree of ink removal either visually or using optical densitymeasurement. Example 2 shows minimal re-solvency of nitrocellulose inkover a period of several minutes wet contact and superior performance toExample 1 in this regard.

In order to illustrate the ability to use the primer of the presentinvention in applications other than paperboard substrates, Example 4was applied with 15 BCM anilox roll onto thin paper substrates <70 gramsper square meter typically used for beer and beverage bottle labels.Once over-printed with SC17604 silver ink using a Meyer #3 bar, thelabel demonstrates comparable metallic brilliance to vacuum metalizedpaper substrate.

All references cited herein are herein incorporated by reference intheir entirety for all purposes.

While the present invention has been described with reference to thespecific embodiments thereof, it should be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processstep or steps, to the objective, spirit and scope of the presentinvention. All such modifications are intended to be within the scope ofthe invention.

1. A primer composition comprising: (a) an acrylic monomer comprisingC—O—C and C═C functional groups; and (b) an acrylic oligomer comprisingC—O—C and C═C functional groups, wherein, said primer composition isenergy curable and the calculated ratio of C—O—C to C═C functionality inthe sum of the acrylic monomer and acrylic oligomer is greater than 1.6.2. The composition of claim 1, wherein the calculated ratio of C—O—C toC═C functionality in the sum of the acrylic monomer and acrylic oligomeris greater than 1.8.
 3. The primer composition of claim 1 when cured andapplied using a Flexiproofer with a 15 bcm anilox on Leneta N2A-3 charthas a dispersive surface energy of at least 37 mN/m; and yields an uppersurface with gloss greater than 55 at 20° angle, and gloss greater than83 at 60° angle.
 4. The primer composition of claim 1 when cured andapplied using a TMI Flexiproofer with a 15 bcm anilox onto a LenetaN2A-3 chart, and then overprinted with SC17604 acetate solvent-basedvacuum metalized pigment silver ink, applied with a Meyer #3 bar, anddried, yields an upper surface with brilliance index of at least 80%. 5.The primer composition of claim 1, wherein there is at least 50%reduction in coating viscosity when measured at 10sec⁻¹ between 25° C.and 45° C.
 6. The primer composition of claim 1 when cured exhibiting atotal visible light reflectance greater than or equal to
 60. 7. Theprimer composition of claim 1 having a static surface tension of up to33 mN/m.
 8. The primer composition of claim 1 exhibiting a 60° glossreduction of less than 10 points and a 20° gloss reduction of less than20 points when changing from 15 bcm to 5 bcm anilox.
 9. The primercomposition of claim 1 exhibiting a 60° gloss difference between thewhite coated area of the BYK Penopac 2817 chart compared with the whiteuncoated area of the chart of less than 2 at 15 bcm and less than 4 at10 bcm.
 10. The primer composition of claim 1 having a viscosity at 45°C. between 17 and 25 cPs.
 11. The primer composition of claim 1, whereineach of the acrylic monomer and acrylic oligomer has a molecular weightgreater than 300 g/mole.
 12. The primer composition of claim 1, whereinthere is at least 50% reduction in coating viscosity when measured at10sec⁻¹ between 25° C. and 45° C., and wherein said primer composition,when cured and applied using a Flexiproofer with a 15 bcm anilox onLeneta N2A-3 chart has a dispersive surface energy of at least 37 mN/m,yields an upper surface with gloss greater than 55 at 20° angle, andgloss greater than 83 at 60° angle.
 13. The primer composition of claim1, wherein there is at least 50% reduction in coating viscosity whenmeasured at 10sec⁻¹ between 25° C. and 45° C., and wherein said primercomposition, when cured and applied using a TMI Flexiproofer with a 15bcm anilox onto a Leneta N2A-3 chart, and then overprinted with SC17604acetate solvent-based vacuum metalized pigment silver ink, applied witha Meyer #3 bar, and dried, yields an upper surface with brilliance indexof at least
 80. 14. A printed article comprising: the primer compositionof claim 1 a primer composition comprising: (a) an acrylic monomercomprising C—O—C and C═C functional groups; and (b) an acrylic oligomercomprising C—O—C and C═C functional groups; wherein the composition isessentially solvent-free; and wherein, said primer composition is energycurable and the calculated ratio of C—O—C to C═C functionality in thesum of the acrylic monomer and acrylic oligomer is greater than 1.6,that when cured exhibits a total visible light reflectance greater thanor equal to
 60. 15. The article of claim 1 being used in packaging. 16.A method of printing an energy curable primer composition comprisingapplying to a substrate the primer composition of claim
 1. 17. Themethod of claim 16 in which the method of printing is flexo or gravure.18. A method for forming a brilliant metallic coated paper materialcomprising: (a) applying a layer of the primer composition of claim 1 toa paper surface of the paper material; (b) curing the layer of theprimer to create an ink receptive interface layer; (c) applying areflective metallic ink including a plurality of reflective particles toat least a portion of the cured primer layer; and (d) drying themetallic ink to form a reflective metallic ink layer on the curedprimer.
 19. The method of claim 18, wherein said primer composition,when cured and applied using a Flexiproofer with a 15 bcm anilox onLeneta N2A-3 chart has a dispersive surface energy of at least 37 mN/m,yields an upper surface with gloss greater than 55 at 20° angle, andgloss greater than 83 at 60° angle.
 20. The method of claim 18, whereinsaid primer composition, when cured and applied using a TMI Flexiprooferwith a 15 bcm anilox onto a Leneta N2A-3 chart, and then overprintedwith SC17604 acetate solvent-based vacuum metalized pigment silver ink,applied with a Meyer #3 bar, and dried, yields an upper surface withbrilliance index of at least 80%.